A. Field of the Invention
The field of the present invention relates generally to adapters for electrically connecting an object to an electrical outlet. In particular, the present invention relates to electrical adapters that are utilized to connect an electrical plug having a first configuration to a receptacle having a second, non-conforming configuration. Even more particularly, this invention relates to such electrical adapters for use with dryers having an electrical cord with either a four or three prong plug configuration that must plug into an outlet having a receptacle with either three or four, respectively, prong-receiving openings.
B. Background
For many years, a large percentage of the population in the United States has primarily used electrically powered dryers for drying clothes, bedding, shoes and other materials. A power cord connects the electric dryer to a source of electrical power, which is typically a wall mounted electrical outlet. Because of the higher electrical load requirements, electric dryers have historically utilized a power cord having a specially configured three-prong plug that is received into a cooperatively configured three-prong receptacle. As a result, most older homes were built with an electrical outlet having a three-prong receptacle in the area where the electric dryer was placed. Since approximately 1996, however, nearly all municipal electrical codes require four-prong receptacles at the electrical outlet to which the dryer connects and use of a cooperatively configured four-prong plug for the electric dryer power cord. In addition to the black and red power wires and the white neutral wire, the four-prong power cord has a green ground wire that does not carry any current and is, instead, grounded back to the junction box or to a separate ground. Inside the dryer, the white neutral wire is not bonded to the chassis and the green wire is grounded from the wiring terminals.
Most homes built prior to 1996 have the three-prong receptacle for the electric dryer, which will not work with the four-prong plugs that are required for newer dryers. Because so many older homes have a three-prong receptacle, most municipal codes allow the dryer to be rewired for use with a power cord having a three-prong plug. Rewiring the electric dryer involves disconnecting the separate ground strap and connecting it to the neutral white wire, which in effect reverts the dryer wiring arrangement to the pre-1996 configuration. As a result, most dryer manufactures configure their dryers to work with either a three-prong or a four-prong power cord. Typically, this requires the manufacturer or retailer to deliver the dryer to the home with both of these power cords and then rewire the dryer at the purchaser's home for use with either a three-prong receptacle or a four-prong receptacle, depending which receptacle is being utilized in the home. Although the home could be rewired to replace the three-prong receptacle with a four-prong receptacle, municipal codes generally do not require such rewiring and, as a result, most homeowners do not want to incur the expense associated with rewiring their home.
There are many different types of electrical adapters which are commonly utilized to interconnect a power cord having a plug of a particular prong configuration with a built-in receptacle having prong openings of a different, non-conforming configuration. Most users are familiar with an electrical adapter that allows a user to plug a three-prong plug, used on most appliances today, to an outlet having a receptacle with only two prong openings. Typically, these adapters wire the third, neutral wire to a grounding wire or clip that is connected to the center screw that attaches the outlet plate to the electrical box in which the receptacle is mounted. As would be readily apparent to those skilled in the art, the use of a straight adapter that connects a four-prong plug to an outlet having a three-prong receptacle would either leave the ground circuit completely open or would require connecting the ground wire to the neutral wire at the outlet. Such a wiring arrangement is likely to violate electrical codes and could be unsafe as it could pose an electrical shock hazard to the user.
What is needed, therefore, is an electrical adapter that safely and simply allows a user to connect a power cord having a four-prong plug to an outlet having a three-prong opening receptacle or allows a user to connect a power cord having a three-prong plug to an outlet having a four-prong opening. The preferred adapter should be configured to allow a user to quickly and without any rewiring of the dryer or the outlet connect a four-prong plug to a receptacle having only three prong openings or allow the user to connect a three-prong plug to a receptacle having four prong openings. The electrical adapter should be configured to safely interconnect the dryer power cord to the outlet so the user will not be exposed to the risk of an electrical shock. Preferably, the electrical adapter will be configured to allow the user, or someone on his or her behalf, to simply connect the more modern four-prong plug on a dryer power cord to the older style outlets having only three prong openings or connect an older three-prong plug on a dryer cord to the newer style outlet having four prong openings.